The present invention relates to a measurement technique; and more particularly to a method and apparatus for measurement of concentrations and accumulated dosages of chemical, nuclear, and biological agents contained in closed environments, such as interiors of aircrafts, buildings, cars, or open environments, such as battlefields, or clouds of hazardous gases moving from place to place, etc.
More in particular, the present invention relates to an apparatus capable of predicting concentrations of vapors at any time during some predetermined mission and the capability of predicting dosages accumulated during the mission time.
Further, the present invention relates to chemical/biological/nuclear detectors in which a Kalman filter, with automatically adjusted filter attributes, is used for low noise prediction of concentrations and accumulated dosages of chemical, biological, nuclear agents, with the purpose of warning/dewarning of people exposed to these agents during a mission time.
Furthermore, the present invention relates to a chemical/biological/nuclear detector where performance is based on an algorithm that accumulatively:
(1) estimates decay (or elevation) rates and amplitude attributes of the chemical/biological vapors in any environment;
(2) estimates chemical/biological vapor dosage accumulated by users in the environment;
(3) predicts the chemical/biological vapor dosage accumulated by the users at the end of a mission;
(4) warns the user when the predicted dosages exceed the myosis level; and
(5) dewarns the users when the concentration of the chemical/biological vapor is so low that for the remaining mission time, the dosage levels will be lower than the myosis level.
The present invention also relates to a simulation model of a chemical/biological/nuclear detector which allows evaluation and analysis of a detector""s performance requirements, sensitivity and accuracy, algorithms, performance of a dosage monitor and a concentration monitor, automation of a detector warning and dewarning method; and measures detoxication of the chemical/biological/nuclear vapors.
The present invention also is related to warning and dewarning methods which would provide the user with advance information prior to harmful effects becoming apparent thereby reducing the harm associated with the user""s exposure to chemical, nuclear, biological agents, while simultaneously decreasing user inconvenience by allowing the user to remove protective gear, such as a mask when such is no longer of necessity during a mission.
In general, it is important to know in an environment containing hazardous chemical, nuclear, or biological agents, how the agents change their concentration over a period of time, and what dosage of such agents have accumulated over a certain period of time in living organisms exposed to the hazardous vapors.
Routinely, chemical, biological, nuclear detectors measure the concentrations of the hazardous material in the environment at predetermined periods of time during a mission. With this approach of making measurements of the concentration of the vapors during the duration of the mission, users exposed to the hazardous vapors in the environment do not know in advance when the dosage of accumulated hazardous material will reach harmful levels which may be detrimental to their health. Moreover, based upon prior procedures, users in the environment containing hazardous substances and carrying masks are not given advance information as to when they can remove their masks responsive to relatively low and harmless concentrations of hazardous vapors extrapolatively calculated for the remainder of the mission.
It is not believed that any mechanisms or techniques have been developed which provide for low noise prediction of concentration and accumulated dosage of chemical, biological, or nuclear vapors in a hazardous environment and which further predict when the users are to use protective clothing such as masks in order to avoid harm associated with chemical/biological agents they are exposed to or alternatively to remove such protective clothing when hazardous vapors are predicted to be at a relatively safe level.
It is an object of the present invention to provide an apparatus and method for measuring a chemical/biological/nuclear agent in an environment which on the basis of a minimum of three measurements of the concentration of the vapor in the environment in question would predict, with a high degree of accuracy, (1) vapor dosage accumulated by users during the mission, (2) warns when the predicted dosages at a certain time point will exceed the myosis level, and (3) dewarns when the concentration is low enough that during the remainder of the mission, the users may avoid using protective clothing such as masks.
It is another object of the present invention to provide an apparatus for measuring concentrations based on Kalman filter predictions, where the parameters of the Kalman filter are adjusted periodically to improve accuracy of predictions.
It is a further object of the present invention to provide a simulated chemical detector and algorithm which is initialized with two initial concentration measurements to estimate a decay (or elevation) rate, as well as the level of chemical vapors in the environment and predicts subsequent measurement of concentration based on Kalman filtered estimates of the decay (or elevation) rate and of the level of chemical vapors in the environment. The algorithm constantly adjusts the Kalman filter parameters or attributes to minimize (or eliminate) the errors due to uncertainties in the system and errors of the measurements. In this manner, the algorithm predicts concentrations for a next subsequent measurement and the accumulated dosage by adding up the dosage for each time increment in order that the total dosage at the end of the mission time is predicted and may be compared with the predetermined harmful dosage level.
In accordance with the teachings of the present invention, an apparatus for measuring behavior parameters, specifically, concentrations of a chemical, biological, or nuclear agent in an environment comprises at least one, but preferably several detectors adapted to measure concentrations of the agent in the environment at predetermined times. A logic block in the algorithm of the present invention receives initial first and second concentration measures and estimates decay (or elevation) rate of the concentration of the agent in the environment.
It is important that a Kalman filter receives the estimated rate change of the concentration of the chemical, biological, and nuclear agent in the environment and, based on these estimates, predicts the next measurement concentration of the agent in the environment.
Detectors then make a next (third) measurement of the concentration of the agent in the environment. The measured concentration and the predicted concentration are compared in order to determine discrepancies therebetween which characterize errors in the system which due to changes in environmental parameters and measurement errors.
Using the magnitude of the discrepancy between the estimated and the measured concentrations, the algorithm further adjusts the Kalman filter parameters or attributes, to increase accuracy of the further predictions of the agent behavior in the environment. The predicted next concentrations are cumulatively added to obtain an accumulated dosage. The algorithm additionally predicts the total dosage at the end of the mission time period.
Warning/dewarning techniques are also included in the simulation. The effects of providing a gas mask to the user is simulated by the algorithm. The total dosage to the user is estimated by accumulating the concentration between the times when a gas mask is removed and being used. Likewise, the effects of removing the gas mask are estimated by accumulating the concentrations after removal of the mask with total accumulated dosages are compared to the myosis dosage level.
The subject invention provides a method of measurement of concentration of a chemical, biological, or nuclear agent including the steps of:
providing an environment represented by a plurality of environment parameters;
measuring first, second and third concentrations of the agent in sequence;
predicting by means of a Kalman filter a predicted concentration of the agent corresponding to the third measurement (the prediction being made based on the first and second concentrations); and
comparing the predicted concentration and the third measured concentrations and calculating system errors causing discrepancies between the predicted and measured concentrations.
Based on the calculated errors, the Kalman filter parameters are adjusted in order to optimize further predictions.
These and other novel features and advantages of this invention will be fully understood from the following detailed description and the accompanying Drawings.